Puncturing a patient into in-body tissue is used in a variety of medical scenes, and among them, blood vessel puncture is performed under ultrasonic guidance. In the blood vessel puncture, a physician visually inspects ultrasonic images acquired by an ultrasonic diagnostic device and showing a cross section of a patient's blood vessel, searches for a desired position on the blood vessel in the ultrasonic images, and places the front end of a puncture needle in the blood vessel. In this process, to acquire ultrasonic images of a blood vessel, the skin above the blood vessel is pressed with an ultrasonic probe to some extent. At this point, however, when the ultrasonic probe is pressed with excessive force, the blood vessel to be punctured undesirably collapses by a large extent, resulting in a difficulty in puncture in some cases. Therefore, to readily puncture the blood vessel, the physician needs to adjust the pressing force of the ultrasonic probe in such a way that the degree of collapse of the blood vessel falls within an adequate range and maintain the state of the blood vessel after the adjustment for a predetermined period. Only visual inspection of acquired ultrasonic images, however, does not allow the physician to clearly grasp the degree of collapse of the blood vessel, and it is therefore difficult to determine whether or not the current pressing state achieved by the ultrasonic probe is so optimized for the patient that the blood vessel is readily punctured.
Patent Literature 1 discloses a system that determines an optimum puncture position where a blood vessel is punctured with a cannula or a needle on the basis of ultrasonic images and automatically inserts the cannula or any other tool in the determined position on the blood vessel.